Alchemy333 Posted February 10, 2023 Share Posted February 10, 2023 I ran diagnostics for the first time on my 90 Coupe. I get a B and R code (h)istory, but ECM stated No Codes. The engine has been a bit on the rough side (only 104k mi)and recently began starting and stalling right after. Replaced plugs, wires, coils, alternator and several sensors recently, entire cooling system... but never got a check engine light. I'm going to be swapping out the harmonic balancer and crank sensor in a few days, but now I'm worried I may need a new ECM. I did notice my head and tail lights flickering last time I drove it as well. I do have LED headlights installed as well. Im the guy restoring the reatta that sat for 10 years and working on the ABS issue in another post... and am no longer able to jump the ABS codes. Is it possible this is linked to the ABS issues? Or am I looking at 2 failing modules? A ground issue? Thanx! Link to comment Share on other sites More sharing options...
Padgett Posted February 10, 2023 Share Posted February 10, 2023 Secondary ignition problems (mine are all Delco now) - coils, plug wires, plugs - will not set codes. I do not recall ever having a EBCM fail. Try R&Ring the connector. 1 Link to comment Share on other sites More sharing options...
2seater Posted February 10, 2023 Share Posted February 10, 2023 (edited) The one issue that can be hard to find, and that is bad data. It may not be far enough off to set a code, but a sensor out of spec can cause issues and this costs nothing to try, Simply unplug the MAF for example and start the engine under the same conditions the stalling occurs. If the stalling improves, it is a hint there is a fault there. It may not run well, but the stalling is the issue. Same can be done for the cam sensor, the intake air temperature and even the O2. Only one at a time and not immediately after each other. Does it help to add a little throttle in case the IAC is a little slow or gummed up? Edited February 10, 2023 by 2seater 1 Link to comment Share on other sites More sharing options...
Alchemy333 Posted February 10, 2023 Topic Author Share Posted February 10, 2023 4 hours ago, 2seater said: The one issue that can be hard to find, and that is bad data. It may not be far enough off to set a code, but a sensor out of spec can cause issues and this costs nothing to try, Simply unplug the MAF for example and start the engine under the same conditions the stalling occurs. If the stalling improves, it is a hint there is a fault there. It may not run well, but the stalling is the issue. Same can be done for the cam sensor, the intake air temperature and even the O2. Only one at a time and not immediately after each other. Does it help to add a little throttle in case the IAC is a little slow or gummed up? No... and didn't act like an IAC issue.. After that day I had trouble, its been starting up fine again. I havnt driven it cuz I dont want to get stranded. I ordered a new fuel filter as well in case it is the issue. Needs to be swapped out anyways. Most everything on the car seems to be original... which is the issue😅🤷♂️ ill be removing both the IAC and MAF for thorough creating and inspection. Simply put, every inch of this car must be gone through. Nearly all plastics and rubbers are brittle, although all inspected wire insulations and connectors seem to be stable (excluding WSS lines which are brittle). California car, no rust... but, sat outdoors in the hot desert for 10yrs. Link to comment Share on other sites More sharing options...
Alchemy333 Posted February 10, 2023 Topic Author Share Posted February 10, 2023 1 Link to comment Share on other sites More sharing options...
Ronnie Posted February 10, 2023 Share Posted February 10, 2023 22 hours ago, Alchemy333 said: I did notice my head and tail lights flickering last time I drove it as well. I do have LED headlights installed as well. I have LED headlights in my GMC truck. Recently I had to replace the battery because it went bad and wouldn't start the engine. Before the battery died I noticed my headlights were flickering some when driving at night and seemed to strobe when starting the engine, even in the daytime. After installing the new battery all the headlight flickering went away and almost all the strobing on startup. The LED lights have always strobed slightly since I installed them when starting the engine. When searching for the reason for the LEDs flickering and strobing I discovered that LED lights respond so quickly to voltage fluctuations it causes them to flicker if they don't get pure DC voltage. My alternator must have been straining trying to keep a bad battery charged and it showed up in the flickering LEDs at night. That's the only explanation I have for why it was happening when the battery was going bad. Your flickering lights might be telling you that you have some type of electrical problem like a bad battery, bad wiring connections or a bad alternator. 2 1 Link to comment Share on other sites More sharing options...
Alchemy333 Posted March 17, 2023 Topic Author Share Posted March 17, 2023 So... ive ran through the electrical and vacuum, replaced nearly every sensor, changed the fuel filter, and still have slightly rough idle and miss at all rpms with NO E CODES. Im concluding ECM at this point. I see these remanufactured ECMs that say require programming. Is this simply PROM swap? Or, would I be better off investing a little more for a plug and play flashed rebuilt/remanufactured. Link to comment Share on other sites More sharing options...
2seater Posted March 18, 2023 Share Posted March 18, 2023 The commonly available service or reman ECM’s generally require the original memcal or eprom to be swapped into the new ECM to keep the factory calibration. I believe their were three different prom numbers for that model year. In diagnostic’s the last item, ed99, is the prom id code and there is a chart for the code in the tutorial area of the ROJ 1 Link to comment Share on other sites More sharing options...
Alchemy333 Posted March 18, 2023 Topic Author Share Posted March 18, 2023 5 hours ago, 2seater said: The commonly available service or reman ECM’s generally require the original memcal or eprom to be swapped into the new ECM to keep the factory calibration. I believe their were three different prom numbers for that model year. In diagnostic’s the last item, ed99, is the prom id code and there is a chart for the code in the tutorial area of the ROJ So I buy a remanufactured ECM... and simply swap eprom? The ones im finding on like carparts.com and rockauto.com simply state... "needs additional programming". Ive had to return plenty of parts based on assumptions and lack of descriptions on these sites. What programming? Or just swap eprom?🤷♂️😅🤷♂️ Link to comment Share on other sites More sharing options...
2seater Posted March 18, 2023 Share Posted March 18, 2023 3 hours ago, Alchemy333 said: So I buy a remanufactured ECM... and simply swap eprom? The ones im finding on like carparts.com and rockauto.com simply state... "needs additional programming". Ive had to return plenty of parts based on assumptions and lack of descriptions on these sites. What programming? Or just swap eprom?🤷♂️😅🤷♂️ The only part that can be programmed is the prom. The ECM itself does not get reflashed or anything like that. Only the removable blue thing under the cover gets moved to the new one. I believe in GM speak it is a Memcal. The now one should have that space empty. The Memcals are getting harder to find so any unused ones should be saved. It will have a four letter code indicating the calibration level. 1 Link to comment Share on other sites More sharing options...
Alchemy333 Posted March 19, 2023 Topic Author Share Posted March 19, 2023 15 hours ago, 2seater said: The only part that can be programmed is the prom. The ECM itself does not get reflashed or anything like that. Only the removable blue thing under the cover gets moved to the new one. I believe in GM speak it is a Memcal. The now one should have that space empty. The Memcals are getting harder to find so any unused ones should be saved. It will have a four letter code indicating the calibration level. Appreciate it brother🙏 Ordered one from rockauto last night which stated upgraded circuitry and simply swap memcal... sound be here Wednesday. Howabout the key recognition and starting procedures? Anything I need to know about? Or, just start her up? Link to comment Share on other sites More sharing options...
2seater Posted March 19, 2023 Share Posted March 19, 2023 7 hours ago, Alchemy333 said: Appreciate it brother🙏 Ordered one from rockauto last night which stated upgraded circuitry and simply swap memcal... sound be here Wednesday. Howabout the key recognition and starting procedures? Anything I need to know about? Or, just start her up? It's no different than starting after the battery has been disconnected, which should be done before plugging and unplugging the ECM. It will be starting from a clean slate and will need to learn the various adjustments needed for optimal operation, which does take a little time. Key recognition is not part of the ECM's duty so it should start and run and then take for a drive. 1 Link to comment Share on other sites More sharing options...
Padgett Posted March 19, 2023 Share Posted March 19, 2023 How boy. In my experience is most likely either dirty injectors (can test in diagnostics) or secondary ignition (Magnavox with plugs gapped .060, should be more like .045), coils, plug wires, or plugs - none of which will set a code. BTW IMNSHO I will never buy anything from RA that might need to be returned. Link to comment Share on other sites More sharing options...
Alchemy333 Posted March 21, 2023 Topic Author Share Posted March 21, 2023 (edited) On 3/19/2023 at 10:26 AM, Padgett said: How boy. In my experience is most likely either dirty injectors (can test in diagnostics) or secondary ignition (Magnavox with plugs gapped .060, should be more like .045), coils, plug wires, or plugs - none of which will set a code. BTW IMNSHO I will never buy anything from RA that might need to be returned. Yah... RA returns are fun😅. Previously changed the plugs, wires, coils, cam and crank sensors, O sensor, fuel filter, checked fuses and vacuum lines. I didn't change ICM as there was no visible defect, I havn't ran through injectors or fuel preassure regulator either yet. My concern is, 90 diagnostics only display codes, that it displays "NO E Codes" yet will display History codes for the 2 other modules. I can pull sensors... still no ECM codes. I just pulled the cover to inspect ECM, and the was only 1 screw holding the panel... which means someone previously been under there. Also found a loose red wire which im uncertain of its function or counterpart. Edited March 21, 2023 by Alchemy333 Link to comment Share on other sites More sharing options...
2seater Posted March 21, 2023 Share Posted March 21, 2023 Only current codes show as codes in the initial display screen, history do not count. They are cleared manually or by battery disconnect. I don't recognize that wire but it appears to be connected to something under your thumb? The ECM has no connections like that, just the two black and one orange harness plug. If you don't get a check engine light, no code is registered. If you disconnect the MAF for example, it probably won't set a code unless the trouble light is on and you check for codes then. If you disconnect and reconnect, it may or may not show a history code. Many sensors have a duration component before it will set a code. For example, something like the ecm registers engine rpm but no MAF reading for 10 seconds or something like that. Did you determine which Memcal you have? GM was constantly tweaking on them to improve or correct possible faults so multiple Proms are available for each year. 1 Link to comment Share on other sites More sharing options...
Alchemy333 Posted March 21, 2023 Topic Author Share Posted March 21, 2023 1 hour ago, 2seater said: Did you determine which Memcal you have? GM was constantly tweaking on them to improve or correct possible faults so multiple Proms are available for each year. Its also a remanufactured. Not sure if original memcal either... as the previous owner had 10+ reattas. Link to comment Share on other sites More sharing options...
Ronnie Posted March 21, 2023 Share Posted March 21, 2023 There is a list of PROMs here on ROJ but I don't see one exactly like yours on it. ECM PROM List I wonder if you might have the wrong one for your car. Maybe someone more knowledgeable than me on PROMS will know. 1 Link to comment Share on other sites More sharing options...
Alchemy333 Posted March 21, 2023 Topic Author Share Posted March 21, 2023 @kdirk ive read your the PROM guy years back. Any advice? Link to comment Share on other sites More sharing options...
2seater Posted March 21, 2023 Share Posted March 21, 2023 That is the latest Prom for 1990 California only. I don't know how they differ from the Federal specs but all years have Cali only Proms. 1 Link to comment Share on other sites More sharing options...
Padgett Posted March 22, 2023 Share Posted March 22, 2023 I have ATYJ 1990 32777 16148015 1228253 8314 8074 EB LN3 3.8 AUTO F79 F79 Transaxle Final Drive 2.97 E Body. (Reatta, Riviera, Eldorado, ...) Link to comment Share on other sites More sharing options...
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